Question

Describe, in detail, the female reproductive cycles. Be sure to include the phases of each cycle and what’s occurring during that phase. In addition, be sure to mention how the cycles are related to one another.

Answer 1

each menstrual cycle has been assumed to be 28 days and the entire cycle can be divided into 4 main phases-

1. menstrual phase- day 1-5

2. follicular phase- day 1-13

3. ovulation phase- Day 14

4. Luteal phase- Day 15-28

Menstrual phase- begins on first day of menstruation and lasts till 5th day of menstrual cycle. Events that occur happen to be- a) uterus sheds its inner lining of soft tissue and blood vessels which exits from body through vulva and about 10-80ml of blood loss occurs which is considered normal. Pitituary glands releases FSH and follicles are immature at this stage in the ovary. The level of hormones estrogen and progesterone levels drops. The thickened lining of uterus which is needed for pregnancy is not needed because the egg ois not fertilized, hence they starts shedding through mucus and blood.

follicular phase- Hypothalamus sends a signal to the pititituary gland to release FSH and this hormone stimulates the ovaries to produce small sacs called follicles. Each follicle contains an immature egg. Maturing follicle increases the estrogen that thickens the lining of uterus and creates a nutrient rich environment for the embryo to grow. Its the proliferative phase of estrous cycle and ends with ovulation.

The main hormones are FSH and GnRH. Follicles starts increasing in size and their will be localized accumulation of fluid in granulosa layers -with a fluid filled cavity called antrum. Primary follicle will develop into secondary, teritiary and finally a graffian follicle. There is a rise in estrogen secretion associated with follicular maturation. Inhibin hormone produced will restrict the no of follicles from maturing.

Ovulation phase- The mature egg is released from the follicles and is ready for fertilization. Rising estrogen levels will stimulate pitituary glands to release LH. (LH surge occurs)The egg travels from fallopian tube towards uterus to get fertilized by the sperm. There will be rise in body temperature and white discharge. It happens on the 14th or middle of menstrual cycle. It lasts for about 24hrs.

Luteal phase- After follicle releases its egg it turns into corpus luteum. It releases progsterone and estrogen. If pregnancy does not occur corpus luteum will shrink away and leads to decreased levels of estrogen and progesterone. The uterine lining will shed during the period to start anoyther menstrual cycle.